Genghis Khan, the fearsome Mongolian warrior of the 13th century, may
have done more than rule the largest empire in the world; according to a
recently published genetic study, he may have helped populate it too.

An international group of geneticists studying Y-chromosome data have
found that nearly 8 percent of the men living in the region of the
former Mongol empire carry y-chromosomes that are nearly identical.
That translates to 0.5 percent of the male population in the world, or
roughly 16 million descendants living today.

The spread of the chromosome could be the result of natural selection,
in which an extremely fit individual manages to pass on some sort of
biological advantage. The authors think this scenario is unlikely. They
suggest that the unique set of circumstances surrounding the
establishment of the Mongol empire led to the spread.

"This is a clear example that culture plays a very big role in
patterns of genetic variation and diversity in human populations," said
geneticist Spencer Wells, one of the 23 co-authors of the paper. "It's
the first documented case when human culture has caused a single
genetic lineage to increase to such an enormous extent in just a few
hundred years."

Legacy of Genghis Khan

To have such a startling impact on a population required a
special set of circumstances, all of which are met by Genghis Khan and
his male relatives, the authors note in the study published in the American Journal of Human Genetics.

Khan's empire at the time of his death extended across Asia, from the
Pacific Ocean to the Caspian Sea. His military conquests were
frequently characterized by the wholesale slaughter of the vanquished.
His descendants extended the empire and maintained power in the region
for several hundred years, in civilizations in which harems and
concubines were the norm. And the males were markedly prolific.

Khan's eldest son, Tushi, is reported to have had 40 sons.
Documents written during or just after Khan's reign say that after a
conquest, looting, pillaging, and rape were the spoils of war for all
soldiers, but that Khan got first pick of the beautiful women. His
grandson, Kubilai Khan, who established the Yuan Dynasty in China, had
22 legitimate sons, and was reported to have added 30 virgins to his
harem each year.

"The historically documented events accompanying the establishment of
the Mongol empire would have contributed directly to the spread of this
lineage," the authors conclude.